Year	% of revenue
1990	11.72644489871771
1991	13.614657440795245
1992	12.122255703831254
1993	10.101164929491109
1994	7.9296293900782615
2000	16.216216216216218
2001	18.093922651933703
2002	8.34805766817751
2003	8.62707915024417
2004	8.02151332504853
2005	10.990938795989761
2006	10.804970363602106
2007	9.766031277642046
2008	22.462643785180358
2009	20.392388055996523
2010	23.32443352875623
2011	17.506906189752293
2012	14.0386870220651
2013	8.442391390043124
2014	8.132218987698375
2015	5.022976429261252
2016	21.045187834584006
2017	4.884177275772949
2020	2.6576194515125815